Apparatus for classifying granular substances



Sept. 23, 1952 M. vARcoE 2,611,486

- APPARATUS FOR CLASSIFYING GRANULAR SUBSTANCES Filed May 15,1949 2 SHEETS-SHEET 1 van/rm 2 SHEETS.-SHEET 2 M. VARCOE APPARATUS FOR CLASS/IFYING GRANULAR SUBSTANCES Filed May 13, 1949 Ila 4.

Sept. 23, 1952 s 7 w E 4.. 4

Patented Sept. 23, 1952 UNITED STATES PATENT F F l'CIE 2,611,486 I APPARATUS FOR CLASSIFYI'N'G GR-ANULAR TSUBSTANGES I .Maurice-Varcoe, Par-Harbour, England, assignor to Cornwall Mills Limited, Par Harbour, England,-a British company Application 'May 13, 194-9, Serial No.9a00'2 In Great Britain May 1 4 1M8 sands, grits and the like, according to particle size.

Up atothe present apparatus :of this character has usually consisted of a sieve through which the granular material is-shaken by a vibratory or tapping action. Where apparatus of this character is not employed, a standard method of classifying simply consists of :a hand treatment of the substance by brushing it through a sieve.

.It is an object of the invention to devise improved apparatus for carrying out the classifying of granular material, according to particle size which apparatus will be simple in use and accurate in regard to the results obtained therewith. It is a more particular object of the invention to provide apparatus for classifying granular material comprising a chamber sieve,

gauze arranged to form part of the walls of said chamber, an air inlet port at the upper end of said chamber, and a pipe connected with :said

air inlet port and extending within such chamher being directed towards the lower end thereof, whereby the outlet end of said pipe lies below :an upper zone of said chamber.

Further and other objects will become apparent from the description that follows and from the appended claims.

iIFor av better understanding of the nature of the invention and to show how the same may be carried into effect, reference will nowbe made to :theaccompanying drawings in which:

Figure 1 is an elevation :of an apparatus made inaccordance with the invention, I

Figure 2 is a longitudinal sectional view of one of the members forming part of the apparatus shown in Figure 1,

Figure 3 is a plan view of Figure 2 being a part section' on the line HI-III of Figure 2,

figure 4 is a 'plan' view :of adust collection unit that may be employed in :conjunctionwith the apparatus shown in Figure 1, and,

Figure '5 is a sectionalelevation of the dust collecting .u-n it shown in Figure 4.

4 Referring first to the construction shown in Figures 1 :to 3, it will be seen that "there is a bench I having uprights 2' secured thereto. These uprights are joined by transverse-members 3 both serving to support .an electric motor =4. The latteris provided with a .fan "whichycauses air :to be sucked :in at an inlet mouth 5 and discharged at :an outlet :mouth 6. The mouth '6 is of annular shape and has internal screwthreading for engagement "with external screwthreading 1 upon :an annular inlet neck 8 (Fig 2), the inlet neck 8 :is formed integral -wi-th ;a pipe-like cylindrical chamber 9, the neck, having an internally extending portion :lyin-g axially within the chamber 19. The suppers-internal :side walls or ithe chamber '9 :are curved,

as at H, so that these walls-appear vin section as two semi-circles (see Fig. '2) Thust'he :upper portion :of the-chambers above the out-let end ofcthe pipe portion It has a zone which :is internally shaped as altsemi-toroid.

.lThe lower periphery of the chamber 9fhas1an :open mouth surroundedrby .a lip or lflangecl2.

:"The upper side of the flange 12 :hasa groove 13 "therein,swhilst the zlowern'side of the i-flange .12 is reb'ated to receivea ring 16. The ring 14 :is of substantially :the same diameter as the chainher 9 so that it appears to Joe in continuation thereof. .Awash'er 15, made .for-examplei from zrubbenis Jinterposerlxbetween the upper edge/of the ring 14 :and rthe'fiange 12. :The ring :Miorms asupport for a sieve gauze :16 secured therein, and thus the ring and the :gauze together constitute a sieve unit. The lower edge ofthering [41S received in the rebate sot areba'ted flange H; the latter .being provided upon the upper :end of a: conduit 4 8. The conduit is of thexsam'e diameteras the ring 14' andwthe. chambers, =so

' thatvall these three separate 'memberspappear to be in general icontinuatlonwhen' seen assembled.

Therconduit 18: has toggle clips .secured::to-:=it. Two of the toggle clips are seen in Figure 51 and it wi-llbbe observed that reach comprises princlosely attached to oneanoth'er in super- ;posed: :co axia-l relation- The-re is-;.a washer 521 disposedas between the slower "edge of them-ing "M and the flange l 'l, so that together withthe 3 washer l5, this washer 2i ensures that the membets are jointed in air-tight relation.

The lower end of the conduit l8 has a separate bag or sleeve 22 of woven material secured thereto with the aid of a clamping collar 23.

In the use of the apparatus described above, material to be sifted or classified is placed upon the sieve gauze Hi. This can be simply achieved by manipulation of the toggle clip fingerpieces to free the hooks l9 from the flange I2. Thereafter the three main members 9, I4 and I8 can be separated for the purpose of introducing the material to be classified into the sieve ring [4. The members may now be reconnected so that the apparatus appears as shown in Figure 1. Upon starting the electric motor 4, air will be blown down the inlet neck Band through the internally extending pipe portion lll. A vortex will be set up in the chamber 9, and the air will encounter the material supported upon the sieve mesh IS. The vortex set upin the chamber 9 will cause the particles upon the sieve to be violently disturbed in such a manner as to allow the particles of small size (i. e. smaller than the openings of the sieve) to pass through the gauze mesh. It is particularly important that the chamber 9 should be conducive to the formation of a vortex, since if air were merely blown under pressure in a direction normal to the plane containing the sieve, the tendency would simply be to clog the sieve. The semitoroidal shaping of the upper interior walls of 'thevortex chamber 9 considerably assists in the desired action.

The fabric sleeve 22 serves to retain the dust which is blown through the sieve gauze it. It may sometimes be convenient to dispense with the sleeve 22 and to connect the conduit 18 with a large diameter pipe which simply opens at some convenient position into the atmosphere. Under certain circumstances if thought desirable, it is possible to enclose the fabric sleeve 22 by a container, which container could then be connected to a suction device which could for example be the air intake 5. Such an arrangement is not however preferred. In practice if dust collection is carried out, then the dust collector shown in Figures 4 and 5 is preferred. In these figures the bench I is shown, the bench being broken away at the top right-hand corner in Figure 4 for purposes merely of illustration. Beneath the bench I there is a compartment having a'lower wall 3| formed with thirty-six regularly disposed apertures. Each aperture is shaped to receive the mouth of a fabric sleeve 32. These sleeves 32 simply hang from the wall 3|, and the lower end of each sleeve is closed by being tied as at 33. By untying the end of a sleeve 32 the latter may be emptied 'as and when required. It will be realised that with the dust collection apparatus of the kind indicated in Figures 4 and 5., there is comparatively little resistance to the outflow of air through the many sleeves 32. At the same time the sleeves efficiently serve to collect fine particles of dust.

The practical employment of the apparatus will require but little skill on the part of the operator.

In order usefully to classify materials, it will be desirableto ensure that a certain standard quantity, for example 10 grams, of material is always placed in the sieve ring upon the sieve gauze. It will further be necessary to ensure that the electric motor is switched on for predetermined constant periods of time. By then measuring the weight of the residue in the sieve, conclusions may be drawn as to the grade of the material that is under test. It may be found desirable to arrange the switch for the motor 4 so that after operation of such switch the motor continues to run only for a predetermined period. Any known suitable form of time switch may be employed.

It will be desirable to have several sizes of sieve gauze available in the use of the apparatus. It has been found that an apparatus such as described above is capable of classifying materials within a range corresponding to the use of a gauze having /8 mesh (i. e. a mesh having openings which are A square) down to a gauze of 325 mesh (1. e. 325 openings per linear inch).

With the employment of a fan for producing the fiow of air into the chamber 9 there may be an undesired tendency for the incoming air to swirl with a considerable component of motion that is rotational about the axis of the chamber 9. It will be clear that the tendency to move particles rotationally in planes parallel to the plane of the sieve, will not in general, be desirable. This will tend merely to erode the sieve without iving effective classification. In practice therefore it is desirable to introduce a baflle B as shown in Figure 2. This baille simply consists of a small plate fixed to lie in the diametral plane containing the axis of the pipe portion [0 and the collar'l. To obtain the maximum benefits of the invention it is necessary that the vortex should be of a nature such that the particles of granular mate rial upon the sieve are disturbed by imparting thereto components of motion which are in directions normal to the plane of the sieve.

I claim:

1. Apparatus for classifying granular substances, comprising a chamber having an open mouth at its lower end, means for supporting a sieve gauze over said mouth, a port disposed at the upper end of said chamber and arranged for connection to a supply of compressed air, a pipelike extension from said port through which the compressed air entering the port must pass, said pipe-like extension being directed towards the mouth of the chamber in order to leave an upper zone of the chamber behind and above the outlet end of said pipe-like extension, and semi-toroidal internal walls connecting the upper end of the internal walls of the chamber with the external walls of said pipe-like extension, said semitoroidal walls lying in said upper zone of the chamber whereby a vortex is produced in the chamber when air is forced into the inlet port.

2. Apparatus for classifying granular substances, comprising a chamber having an open mouth at its lower end, a sieve holder, sieve gauze supported in said holder, a surface upon said sieve holder for close engagement with the mouth of said chamber, a conduit, a second surface upon said sieve holder for close engagement'with said conduit, an air inlet port at the upper end of said chamber, a pipe-like extension from said port lying within said chamber and directed towards the said gauze, the outlet end of said pipelike extension having above and behind it a zone of the chamber and semi-toroidal internal walls connecting the upper end of the internal walls of said chamber with the external walls of said pipe-like extension, said semi-toroidal walls lying in said zone of the chamber whereby a vortex is produced in the chamber when air is forced into the inlet port, the vortex serving to disturb granular substance that may be placed upon said sieve gauze thereby causing granular particles smaller than the sieve mesh to pass therethrough UNITED STATES PATENTS into said conduit. Number Name Date 3. Apparatus as claimed in claim 2, and fur- 1 810 935 Wood June 23 1931 ther comprising releasable grippingmeans ar- 2002974 f g' g' May 1935 ranged to hold the chamber, sieve holder and 5 2202189 Cotton Jr gi May 1940 conduit in closely attached relation.

MAURICE VARCOE OTHER REFERENCES An Apparatus for the Separation of Grit and REFERENCES CITED Coarse Particles From Fine Powders, by Gallie' The following references are of record. in the 10 and Porritt. W. Heifer and Sons Ltd., Camfile of this patent: bridge, England, 1926 (reprinted from August issue of "I. R. I. Transactions). 

